The state of the art in achieving a radio's desired operating characteristics, or "personality" as it is commonly known, has readily advanced over the last five years. In the past, a radio's personality was determined at the time of assembly by combining unique components into a working unit. This is an expensive and inefficient method for manufacturing a multiplicity of models because of the large inventory that must be maintained in order to fulfill each customer order in a timely fashion. With the advent of high capacity digital decimal electronic signalling schemes in the paging industry, the need arose for a more efficient and cost effective means for manufacturing portable selective call radio receivers and transmitters. It was during the mid 1970's that the technology for the use of nichrome code plugs as a memory device became practical. The idea of a using pre-programmed fusible link code plug that could be read by a custom integrated circuit or a microprocessor revolutionized the paging industry. By using a nichrome code plug, the manufacturer could now design a fairly generic radio that could be configured to provide a wide variety of options by reading the state (electrical open or short circuits) of predetermined fusible links within the code plug and determining the desired operating mode accordingly. Nichrome code plugs were not without their problems as they are a one shot deal, that is, once you "blow" the links in the code plug, the radio's options relating to those links that are now fixed and cannot revert to their previous states. The fact that the links are permanently melted apart leads to the obvious conclusion that if you want to reprogram radio functions at a later date, you must replace the used code plug with a new one and reprogram the radio. Another problem with nichrome code plugs is that a substantial amount of electrical current is required to "blow" the links. Because of this, the radio itself is not able to program the code plug while installed. External programmers had to be developed to program and verify the nichrome code plugs.
With the development of low voltage EEPROM's (electrically erasable programmable read only memories) and other low power/low voltage memory devices such as battery powered static random access memory, portable radio devices can now be designed to take advantage of the permanent installation of these memory devices. They serve the same function as the nichrome code plugs but allow the manufacturer to further reduce the unit's cost to the customer by eliminating the need to replace the code plug. These devices also improve the reliability of the design by eliminating the temporary interconnects used to contact nichrome code plugs.
Another problem facing designers of portable radio products in the area of electronically configurable options is that all existing products require a microprocessor to control and interface the programming signals and data to the code plug.
Thus, what is needed is a method for recognizing and programing with minimal user intervention, a portable communication device's code plug to provide a dynamically reconfigurable personality for the portable communication device.